Introduction
Normal T-lymphocytes express either αβ or γδ T-cell receptors, while γδ
T-cells comprise 0.5%–10% of total T-cells with variable distribution
in mucosa, spleen, lymph node and other sites, that play critical roles
of innate and adaptive immunity.1 The physiological
development and immunophenotype of γδ T-cells are different from αβ
T-cells.2 For instance, subsets of γδ T-cells are less
dependent on thymic microenvironment and may arise
extrathymically.1-3 The γδ T-cells express CD3,
variable CD5, variable CD56 and CD57, while they are often negative for
CD4 and CD8.
T-cell lymphomas (TCLs) account for about 12% of the total lymphoid
tumors, and comprise over 20 distinct entities in the World Health
Organization (WHO) classifications.4 TCLs are
extremely rare in children. Aside from T-lymphoblastic and anaplastic
large cell lymphomas; the majority of TCLs originate from αβ T-cells and
only few arise from γδ T cells, 4-6 including primary
cutaneous γδ T-cell lymphoma (PCGDTCL), hepatosplenic T-cell lymphoma
(HSTCL), and monomorphic epitheliotropic intestinal T-cell lymphoma
(MEITL).4 Patients with these types of γδ TCLs appear
to have an aggressive clinical course and poor outcome despite
aggressive chemotherapy and/or additional treatments.4Occasional γδ T-cell lymphoma cases are limited to the subcutis and show
a less aggressive clinical course.3,7-10 Further, some
cutaneous and subcutaneous TCLs and non-malignant skin conditions may
demonstrate an increase in γδ T-cells, with uncertain
significance.2-4,11,12
Hence, our current knowledge of γδ TCLs is mostly based on adult
patients; and the pathological and clinical studies of pediatric γδ TCLs
are scarce.13 Moreover, the spontaneous regression of
cutaneous γδ T-cell clonal proliferation has been reported in
inflammatory and in non-neoplastic disorders.14 In
this study, we report the pathological and clinical features of three
unusual patients from this unique pediatric multi-disciplinary cutaneous
lymphoma clinic.